Conventionally, there has been known a high-pressure dome type compressor as disclosed in, for example, Japanese Patent Laid-Open Publication No. SHO 60-224988. In this high-pressure dome type compressor, a suction pipe is connected to a compression section, compressed gas compressed by the compression section is once discharged into the casing and then discharged out of the casing via an outside discharge pipe.
More specifically, in the conventional high-pressure dome type compressor, as shown in FIG. 2, a compression section E comprising a fixed scroll B fixed to a housing A disposed in a casing F and a movable scroll D to be driven by a drive shaft C of a motor M is internally provided airtight within the closed casing F. A suction pipe G is connected to the fixed scroll B, and a discharge port H opened into the casing F is defined in the fixed scroll B.
In the movable scroll D, there is defined a boss D1 to which is fitted an eccentric shaft portion C1 of the drive shaft C that is connected to the motor M, so that the movable scroll D will be eccentrically rotated as the drive shaft C rotates. The drive shaft C is supported with a bearing by the housing A, while oil in an oil reservoir J at the bottom of the casing F is pumped up through an oil feed passage C2 defined in the drive shaft C so as to be fed to the bearing portion and boss D1's sliding portion of the housing A.
Then, gas sucked from the suction pipe G into the compression section E is compressed in a compression chamber K defined between the scrolls B, D, then discharged into the casing F through the discharge port H defined at the center of the fixed scroll B, and thereafter discharged out of the casing F via an outside discharge pipe L.
For the conventional high-pressure dome type compressor, there is a need of cooling oil because the oil fed to the bearing portion through the oil feed passage C2 of the drive shaft C, which has become high in temperature due to frictional heat, is returned to the oil reservoir J of the casing F. However, the cooling of oil in the oil reservoir J is usually implemented merely by naturally cooling only the surface of the oil reservoir J by heat exchange with the discharge gas which has been discharged into the casing F, not by aggressively cooling the oil enough. Thus, there has been a problem in that seizure may occur to the sliding portions.
In operating ranges in which the amount of refrigerant circulation decreases, there has been another problem that oil cannot be cooled up by discharge gas so that the oil becomes an abnormally high temperature, causing a deterioration of the oil.
As a solution for this, it might be conceived to implement the cooling of oil by aggressively putting the discharge gas into contact with the surface of the oil reservoir. With this solution applied, however, the oil would be disturbed by the discharge gas being blown against the oil reservoir, resulting in a problem of so-called oil rise that the oil is discharged along with gas.
The present invention has been developed in view of the above described problems and has for its essential object to provide a high-pressure dome type compressor capable of successfully cooling the oil fed to sliding portions by implementing heat exchange between the discharge gas and the oil fed to the sliding portions, without causing any oil rise.